This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 from an application for METHOD FOR CONFIGURING NETWORK INTERFACE CIRCUIT IN INTEGRATED SERVICES DIGITAL NETWORK KEYPHONE SYSTEM earlier filed in the Korean Industrial Property Office on the 28th of February 1997 and there duly assigned Ser. No. 6551/1997.
1. Field of the Invention
The present invention relates to a keyphone system and, in particular, to a technique for configuring a network interface circuit for interfacing an analog keyphone system to an integrated services digital network (hereinafter, referred to as an xe2x80x9cISDNxe2x80x9d).
2. Description of the Related Art
While a typical keyphone system has been used by being interfaced with a public switched telephone network (hereinafter, referred to as a xe2x80x9cPSTNxe2x80x9d), it has also been recently used with an ISDN. Herein, the keyphone system being interfaced with the ISDN is conventionally called an ISDN keyphone system. The ISDN keyphone system includes a basic rate interface (hereinafter referred to as a xe2x80x9cBRIxe2x80x9d) of the ISDN and a network interface circuit. Therefore, the network interface circuit is generally considered as the BRI trunk.
The BRI trunk, used as a device for interfacing the analog keyphone system with the BRI, performs the ISDN protocol. Also, the BRI is used as an S/T interface of the basic rate interface regulated in the ISDN, that is, an interface line between the ISDN and a terminal, including 2B+D channels comprised of two B channels and one D channel. The B channel is used for transmission of voice and data information with the transmission rate of 64 Kbps and the D channels are used for transmission of a control signal with the transmission rate of 16 Kbps. In this BRI trunk, a function program for supporting the ISDN protocol is installed within a read only memory (hereinafter, referred to as a xe2x80x9cROMxe2x80x9d) located in the BRI trunk.
Meanwhile, the ISDN protocol depends upon the country or network in most cases. Therefore, when different countries or the networks operate with the ISDN keyphone system, the function program for performing the ISDN protocol by the BRI trunk of the corresponding ISDN keyphone system has to be varied accordingly. Consequently, it is necessary for the ROM included in the BRI trunk to contain a function program in conformity with the corresponding country or network.
As stated hereinafter, since the function program for performing the ISDN protocol for a specific country or a specific network is included in the ROM of the BRI trunk, there is a problem in that the ROM included in the BRI trunk must be replaced with a new ROM in conformity with the corresponding country or network whenever the country or network used by the keyphone system is changed.
The following patents each disclose features in common with the present invention but do not teach or suggest the specifically recited technique for configuring a network interface circuit in an integrated services digital network keyphone system of the present invention: U.S. Pat. No. 5,666,349 to Petri, entitled Method For Controlling Components Of A Communication System, U.S. Pat. No. 5,442,630 to Gagliardi et al., entitled lSDN Interfacing Of Local Area Networks, U.S. Pat. No. 5,574,861 to Lorvig et al., entitled Dynamic Allocation Of B-Channels In ISDN, U.S. Pat. No. 5,481,598 to Bergler et al., entitled Subscriber Terminal For ISDN Network, U.S. Pat. No. 5,070,524 to Mano, entitled Telephone System, U.S. Pat. No. 5,617,630 to Feinberg et al., entitled Interface For A Data Telephone And Data Terminal In A Digital Telephone System, U.S. Pat. No. 5,655,001 to Cline et al., entitled Wireless Telecommunication System Using Protocol Conversion For Signaling Between Base Stations And Land Based Switches, U.S. Pat. No. 5,062,108 to Bales et al., entitled ISDN Codeset Conversion, U.S. Pat. No. 5,239,542 to Breidenstein et al., entitled Time Division Multiplex Switching System For Interconnecting Telephone Circuits Which Operate In Accordance With Different Signaling Systems And Call Formats, U.S. Pat. No. 5,278,972 to Raker et al., entitled Communication System For Converting ISDN Signaling Protocol Between Local And Public Network Having First Group Of Mandatory Elements And Second Group Of Non-Mandatory Elements, U. S. Pat. No. 5,412,660 to Chen et al., entitled ISDN-To ISDN Communication Via Satellite Microwave Radio Frequency Communications Link, and U.S. Pat. No. 5,652,782 to Hughes-Hartogs, entitled Digital Telephone Overcoming International Incompatibilities.
It is an object of the present invention to provide a technique for configuring a network interface circuit capable of being commonly used, in all countries or networks which have different ISDN protocols, with only one BRI trunk.
In order to achieve the above object, the present invention comprises a technique for configuring a network interface circuit in an integrated services digital network keyphone system, comprising the steps of: first storing beforehand in a read only memory(ROM) of the network interface circuit all function programs for supporting an integrated services digital network protocol for a country and a network which will be used by the keyphone system, selecting a function program from among the function programs stored in the ROM corresponding to the country and kind of network to be operated upon initialization, and setting the selected program as the function program to be executed.